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INFLUENCE OF HOT WOEKING ON" STEEL.
taking at random from the records of The Pennsylvania Steel Company the tests on fifty bars of small angles and fifty bars of large angles of each different thickness, of common Bessemer steel, running from .07 to .10 per cent, of phosphorus.
For making the 6"x6" angles, a bloom 8"x9%" was rolled from a 16"x20" ingot, but all other sizes were made from a 7%-inch square bloom which was cogged from a 16"xl6" ingot. The term "small" angles includes 4^"x3", 4"x4", and all smaller sizes down to and including 3"x3"; while the "large" embraces from 5"x3" to 6"x6", inclusive. The finished area of the smaller bars is such a small part of the original bloom that the reduction may be considered uniform iCor them all, thus giving a fairly valid basis of 'comparison for the different thicknesses, while the columns "large" and "small" should show the effect of a varying amount of work on a piece of given thickness.
Comparison of Ultimate Strength of Bars Eolled from Test. Ingots Six Inches Square, and Test-Pieces Cut from Angles of Different Thicknesses Eolled from the same Heats.
Elastic limit ; Iba. Ultimate strength; Elastic ratio;
OQ •U per square inch. Ibs. per square inch. per cent.
Thickness of . -3 « a) fl •H 43 ri •H to
angle; in inches. ofl •2s S d 1. g ^ . bo • a , d „
,08 0-w o o -ftsi , ii •S'S) •M (m I-S
E » £" w'H W* 3"" w'H *$ o to d W^ «.«
A and % 89 42270 41300 970 60200 60190 10 70.28 68.62
jk and J4 46 48070 40170 2900, 61860 60660 700 70.1» 66.22
A and % 87 42990 89710 8280 62980 61520 1410 68.81 64.55
It will be noted that the small-sized angles give slightly better results on elongation, but the difference is trifling, while in neither the elastic ratio nor the reduction of area is there any marked superiority. - The results indicate 'that when the amount of work is large, the exact percentage is of little consequence.
The ultimate strength decreases in the thicker angles, but it is not proven that the variation is due entirely to the thickness, for it may be that the heats which were rolled into thick sizes did happen to be of lower strength, but as all the heats were made in the same way, and as both large and small sizes follow the same law, and as